Outcome of relapse after allogeneic HSCT in children with ALL enrolled in the ALL-SCT 2003/2007 trial

Disease Status and Interval between Hematopoietic Cell Transplantations Predict Outcome of Pediatric Patients Who Undergo Subsequent Transplantation for Relapsed Hematologic Malignancy

Patients with hematologic malignancies who relapse after allogeneic hematopoietic cell transplantation (HCT) have a poor prognosis. Although proceeding to subsequent HCT can provide potential for long-term survival, there are limited data to guide which patients are most likely to benefit and which HCT strategies are best in this heavily pretreated population. The goals of this study were to describe the clinical outcomes of subsequent HCT in pediatric patients with relapsed hematologic malignancies in a cohort enriched for haploidentical donors, and to evaluate the associations of patient-, disease-, and treatment-related factors with survival. We retrospectively evaluated patients who underwent a subsequent HCT for management of post-HCT relapse at a single institution between 2000 and 2021. Among 106 patients who underwent a second allogeneic HCT, the 1-year event-free survival (EFS) was 34% and 1-year overall survival (OS) was 46%, with a 5-year EFS of 26% and 5-year OS of 31%. Only disease-related factors were associated with outcome after second HCT-specifically, the interval between HCTs and the presence or absence of active disease at the time of HCT. In this cohort, patient- and treatment-related factors were not associated with differences in EFS or OS. Patients undergoing a third or fourth HCT (n = 13) had comparable survival outcomes to those undergoing a second HCT. Our experience highlights that a subsequent HCT has curative potential for a subset of patients who relapse after HCT, including those who undergo a subsequent HCT from a haploidentical donor. Although relapse and treatment-related toxicities remain major challenges, our study indicates that achieving complete remission prior to subsequent HCTs has the potential to further improve outcomes.

Base-Edited CAR7 T Cells for Relapsed T-Cell Acute Lymphoblastic Leukemia

BACKGROUND

Cytidine deamination that is guided by clustered regularly interspaced short palindromic repeats (CRISPR) can mediate a highly precise conversion of one nucleotide into another - specifically, cytosine to thymine - without generating breaks in DNA. Thus, genes can be base-edited and rendered inactive without inducing translocations and other chromosomal aberrations. The use of this technique in patients with relapsed childhood T-cell leukemia is being investigated.

METHODS

We used base editing to generate universal, off-the-shelf chimeric antigen receptor (CAR) T cells. Healthy volunteer donor T cells were transduced with the use of a lentivirus to express a CAR with specificity for CD7 (CAR7), a protein that is expressed in T-cell acute lymphoblastic leukemia (ALL). We then used base editing to inactivate three genes encoding CD52 and CD7 receptors and the β chain of the αβ T-cell receptor to evade lymphodepleting serotherapy, CAR7 T-cell fratricide, and graft-versus-host disease, respectively. We investigated the safety of these edited cells in three children with relapsed leukemia.

RESULTS

The first patient, a 13-year-old girl who had relapsed T-cell ALL after allogeneic stem-cell transplantation, had molecular remission within 28 days after infusion of a single dose of base-edited CAR7 (BE-CAR7). She then received a reduced-intensity (nonmyeloablative) allogeneic stem-cell transplant from her original donor, with successful immunologic reconstitution and ongoing leukemic remission. BE-CAR7 cells from the same bank showed potent activity in two other patients, and although fatal fungal complications developed in one patient, the other patient underwent allogeneic stem-cell transplantation while in remission. Serious adverse events included cytokine release syndrome, multilineage cytopenia, and opportunistic infections.

CONCLUSIONS

The interim results of this phase 1 study support further investigation of base-edited T cells for patients with relapsed leukemia and indicate the anticipated risks of immunotherapy-related complications. (Funded by the Medical Research Council and others; ISRCTN number, ISRCTN15323014.).

Exploring the mechanism of physcion-1-O-β-D-monoglucoside against acute lymphoblastic leukaemia based on network pharmacology and experimental validation

Objective

To explore the mechanism of PG against acute lymphoblastic leukaemia (ALL) by network pharmacology and experimental verification in vitro.

Methods

First, the biological activity of PG against B-ALL was determined by CCK-8 and flow cytometry. Then, the potential targets of PG were obtained from the PharmMapper database. ALL-related genes were collected from the GeneCards, OMIM and PharmGkb databases. The two datasets were intersected to obtain the target genes of PG in ALL. Then, protein interaction networks were constructed using the STRING database. The key targets were obtained by topological analysis of the network with Cytoscape 3.8.0 software. In addition, the mechanism of PG in ALL was confirmed by protein‒protein interaction, gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. Furthermore, molecular docking was carried out by AutoDock Vina. Finally, Western blotting was performed to confirm the effect of PG on NALM6 cells.

Results

PG inhibited the proliferation of NALM6 cells. A total of 174 antileukaemic targets of PG were obtained by network pharmacology. The key targets included AKT1, MAPK14, EGFR, ESR1, LCK, PTPN11, RHOA, IGF1, MDM2, HSP90AA1, HRAS, SRC and JAK2. Enrichment analysis found that PG had antileukaemic effects by regulating key targets such as MAPK signalling, and PG had good binding activity with MAPK14 protein (-8.9 kcal/mol). PG could upregulate the expression of the target protein p-P38, induce cell cycle arrest, and promote the apoptosis of leukaemia cells.

Conclusion

MAPK14 was confirmed to be one of the key targets and pathways of PG by network pharmacology and molecular experiments.

Late relapse after hematopoietic stem cell transplantation for acute leukemia: a retrospective study by SFGM-TC

Late relapse (LR) after allogeneic hematopoietic stem cell transplantation (AHSCT) for acute leukemia is a rare event (nearly 4.5%) and raises the questions of prognosis and outcome after salvage therapy. We performed a retrospective multicentric study between January 1, 2010, and December 31, 2016, using data from the French national retrospective register ProMISe provided by the SFGM-TC (French Society for Bone Marrow Transplantation and Cellular Therapy). We included patients presenting with LR, defined as a relapse occurring at least 2 years after AHSCT. We used the Cox model to identify prognosis factors associated with LR. During the study period, a total of 7582 AHSCTs were performed in 29 centers, and 33.8% of patients relapsed. Among them, 319 (12.4%) were considered to have LR, representing an incidence of 4.2% for the entire cohort. The full dataset was available for 290 patients, including 250 (86.2%) with acute myeloid leukemia and 40 (13.8%) with acute lymphoid leukemia. The median interval from AHSCT to LR was 38.2 months (interquartile range [IQR], 29.2 to 49.7 months), and 27.2% of the patients had extramedullary involvement at LR (17.2% exclusively and 10% associated with medullary involvement). One-third of the patients had persistent full donor chimerism at LR. Median overall survival (OS) after LR was 19.9 months (IQR, 5.6 to 46.4 months). The most common salvage therapy was induction regimen (55.5%), with complete remission (CR) obtained in 50.7% of cases. Ninety-four patients (38.5%) underwent a second AHSCT, with a median OS of 20.4 months (IQR, 7.1 to 49.1 months). Nonrelapse mortality after second AHSCT was 18.2%. The Cox model identified the following factors as associated with delay of LR: disease status not in first CR at first HSCT (odds ratio [OR], 1.31; 95% confidence interval [CI], 1.04 to 1.64; P = .02) and the use of post-transplantation cyclophosphamide (OR, 2.23; 95% CI, 1.21 to 4.14; P = .01). Chronic GVHD appeared to be a protective factor (OR, .64; 95% CI, .42 to .96; P = .04). The prognosis of LR is better than in early relapse, with a median OS after LR of 19.9 months. Salvage therapy associated with a second AHSCT improves outcome and is feasible, without creating excess toxicity.

Genome-edited allogeneic donor "universal" chimeric antigen receptor T cells

αβ T cell receptor (TCRαβ) T cells modified to express chimeric antigen receptors (CAR), are now available as authorized therapies for certain B-cell malignancies. However the process of autologous harvest and generation of patient-specific products is costly, with complex logistics and infrastructure requirements. Premanufactured banks of allogeneic donor-derived CAR T cells could help widen applicability if the challenges of HLA-mismatched T-cell therapy can be addressed. Genome editing is being applied to overcome allogeneic barriers, most notably, by disrupting TCRαβ to prevent graft-versus-host disease, and multiple competing editing technologies, including CRISPR/Cas9 and base editing, have reached clinical phase testing. Improvements in accuracy and efficiency have unlocked applications for a wider range of blood malignancies, with multiplexed editing incorporated to target HLA molecules, shared antigens and checkpoint pathways. Clinical trials will help establish safety profiles and determine the durability of responses as well as the role of consolidation with allogeneic transplantation.

The frequencies of lymphocyte subsets on "day 30″ correlate with the clinical outcome of pediatric hematopoietic stem cell transplantation

We aimed to determine the relationship between lymphocyte subsets on day 30 (D30) and prognosis after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in children. We retrospectively examined the clinical outcomes and lymphocyte subsets on D30 after allo-HSCT in 115 pediatric patients at the Children's Hospital of Soochow University between January 2016 and June 2019. Measurements were performed using flow cytometry on D30. Lymphocyte subsets were compared among the umbilical cord blood (UCB) (n = 22), HLA-matched sibling donor (MSD) (n = 14), haploidentical donor transplantation (HID) (n = 57), and unrelated donor transplantation (UD) (n = 22) groups. The relationships between the frequencies and counts of lymphocyte subsets and clinical outcomes were analyzed. T and B cell counts were the highest in the MSD group compared to the other groups, and natural killer cell counts were the highest in the UCB group. Lymphocyte subsets on D30 after allo-HSCT were correlated with the occurrence of acute (aGVHD) and chronic graft versus host disease (cGVHD). A high frequency of B cells (≥4.65%) was associated with the development of severe aGVHD. High frequencies of CD4⁺T (≥10.25%) were correlated with extensive cGVHD. Moreover, a high frequency of CD4⁺T cells (≥9.80%) was correlated with GVHD-free and failure-free survival (GFFS) after allo-HSCT. However, on D30, there were no statistically significant correlations between viral infections and lymphocyte subsets. The frequencies of lymphocyte subsets on D30 after allo-HSCT are good indicators of prognosis after allo-HSCT in children.

Efficacy and safety of blinatumomab in children with relapsed/refractory B cell acute lymphoblastic leukemia: A systematic review and meta-analysis

Objectives: Several clinical trials have been conducted to evaluate the effects of blinatumomab in childhood B cell acute lymphoblastic leukemia (B-ALL). We conducted this meta-analysis to validate the efficacy and safety of blinatumomab in pediatric patients with relapsed/refractory B-ALL (R/R B-ALL). Methods: We searched and investigated all relevant studies in the PubMed, Web of Science, Embase, and Cochrane Library databases. The primary outcomes were complete response (CR), overall survival (OS), event free survival (EFS), minimal residual disease (MRD) response, allogeneic hematopoietic stem cell transplantation (allo-HSCT) and were calculated separately for randomized controlled trials (RCTs) and single-arm studies. The secondary end points were adverse effects (AEs) and the relapse rate. The Cochrane, bias assessment tool, was used to assess the risk of bias in RCTs. The methodological quality of single-arm studies was assessed using the methodological index for non-randomized studies (MINORS) tool. Results: The meta-analysis included two RCTs and 10 single-arm studies, including 652 patients in total. Our study showed that in the single-arm studies, the combined CR rate was 0.56 (95% confidence interval (CI): 0.45 -0.68), the odds ratios (ORs) of OS was 0.43 (95% CI 0.32 -0.54), the EFS rate was 0.30 (95% CI: 0.20 -0.40), the MRD response was 0.51 (95% CI: 0.34 -0.68), allo-HSCT rate was 0.62 (95% CI: 0.50 -.74), the AE rate was 0.65 (95% CI: 0.54 -0.76) and the relapse rate was 0.32 (95% CI: 0.27 -0.38). In the RCTs, the blinatumomab-treated group compared with the chemotherapy group had a combined OS rate of 0.12 (95% CI: 0.05 -0.19) and an EFS rate of 2.16 (95% CI: 1.54 -3.03). The pooled MRD response rate was 4.71 (95% CI:2.84 -7.81), allo-HSCT was 3.24 (95% CI: 1.96 -5.35), the AE rate was 0.31 (95% CI: 0.16 -0.60), and the relapse rate was 0 .69 (95% CI: 0.43 -1.09). Conclusion: According to this meta-analysis, blinatumomab shows potent therapeutic efficacy and limited AEs in children with R/R B- ALL. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42022361914.

Combining blinatumomab and donor lymphocyte infusion in B-ALL patients relapsing after allogeneic hematopoietic cell transplantation: a study of the SFGM-TC

Relapsed B-cell acute lymphoblastic leukemia (B-ALL) after allogeneic stem cell transplantation (allo-HCT) still represents a major concern with poor outcomes. The aim of this study is to compare the efficacy and safety of blinatumomab and donor lymphocyte infusion (DLI) versus blinatumomab alone in this setting. This is a multicenter retrospective study from centers of SFGM-TC. All transplanted patients who received blinatumomab salvage therapy were included. Patients who received DLI from 1 month before to 100 days after the starting of blinatumomab were included in the blina-DLI group. Seventy-two patients were included. Medium follow-up was 38 months. Fifty received blinatumomab alone and 22 the association blinatumomab-DLI. Two-year overall survival (OS) was 31% in the blinatumomab group and 43% in the blinatumomab-DLI group (p = 0.31). Studying DLI as a time dependent variable, PFS did not significantly differ between the 2 groups (HR:0.7, 95% CI: 0.4-1.5). In multivariate analysis, DLI was not a prognostic factor for OS, progression-free survival and progression/relapse incidence. Adverse events and graft-versus-disease rates were comparable in the 2 groups. In conclusion, adding DLI between 1 month before and 100 days after start of blinatumomab is safe and does not seem to improve outcomes in B-ALL patients who relapsed after allo-HCT.

Early relapse prediction after allogeneic hematopoietic stem cell transplantation for acute lymphoblastic leukemia (ALL) using lineage-specific chimerism analysis

Relapse is a major cause of treatment failure after hematopoietic stem cell transplantation (HSCT) for acute leukemia. Here, we report a monocentric retrospective study of all HSCTs for B cell acute lymphoblastic leukemia (ALL) performed during the years 2005-2021 (n = 138, including 51 children), aiming to identify the optimal use of lineage-specific recipient-donor chimerism analysis for prediction of relapse. In adults, relapse was associated with increased recipient chimerism in CD3⁺ bone marrow cells sampled at least 30 days before a relapse. Relapse could be predicted with a sensitivity of 73% and a specificity of 83%. Results were similar for children but with a higher recipient chimerism cutoff. Additionally, adults that had at least one chimerism value <0.12% in CD3⁺ peripheral blood cells within the first 60 days after HSCT had 89% probability of being relapse-free after 2-years compared to 64%. Results were similar for children but again necessitating a higher chimerism cutoff. These results suggest that high-sensitive lineage-specific chimerism analysis can be used for (1) early ALL relapse prediction by longitudinal chimerism monitoring in CD3⁺ bone marrow cells and (2) relapse risk stratification by analyzing CD3⁺ blood cells early post-HSCT.

Phase 1 clinical trial of CRISPR-engineered CAR19 universal T cells for treatment of children with refractory B cell leukemia

Genome editing of allogeneic T cells can provide "off-the-shelf" alternatives to autologous chimeric antigen receptor (CAR) T cell therapies. Disruption of T cell receptor α chain (TRAC) to prevent graft-versus-host disease (GVHD) and removal of CD52 (cluster of differentiation 52) for a survival advantage in the presence of alemtuzumab have previously been investigated using transcription activator-like effector nuclease (TALEN)-mediated knockout. Here, we deployed next-generation CRISPR-Cas9 editing and linked CAR expression to multiplexed DNA editing of TRAC and CD52 through incorporation of self-duplicating CRISPR guide RNA expression cassettes within the 3' long terminal repeat of a CAR19 lentiviral vector. Three cell banks of TT52CAR19 T cells were generated and cryopreserved. A phase 1, open-label, non-randomized clinical trial was conducted and treated six children with relapsed/refractory CD19-positive B cell acute lymphoblastic leukemia (B-ALL) (NCT04557436). Lymphodepletion included fludarabine, cyclophosphamide, and alemtuzumab and was followed by a single infusion of 0.8 × 106 to 2.0 × 106 CAR19 T cells per kilogram with no immediate toxicities. Four of six patients infused with TT52CAR19 T cells exhibited cell expansion, achieved flow cytometric remission, and then proceeded to receive allogeneic stem cell transplantation. Two patients required biological intervention for grade II cytokine release syndrome, one patient developed transient grade IV neurotoxicity, and one patient developed skin GVHD, which resolved after transplant conditioning. Other complications were within expectations, and primary safety objectives were met. This study provides a demonstration of the feasibility, safety, and therapeutic potential of CRISPR-engineered immunotherapy.

Tisagenlecleucel for relapsed/refractory acute lymphoblastic leukemia in the Irish healthcare setting: cost-effectiveness and value of information analysis

OBJECTIVES

This study evaluates the cost-effectiveness of tisagenlecleucel (a CAR T-cell therapy), versus blinatumomab, for the treatment of pediatric and young adult patients with relapsed/refractory acute lymphoblastic leukemia (R/R ALL) in the Irish healthcare setting. The value of conducting further research, to investigate the value of uncertainty associated with the decision problem, is assessed by means of expected value of perfect information (EVPI) and partial EVPI (EVPPI) analyses.

METHODS

A three-state partitioned survival model was developed. A short-term decision tree partitioned patients in the tisagenlecleucel arm according to infusion status. Survival was extrapolated to 60 months; general population mortality with a standardized mortality ratio was then applied. Estimated EVPI and EVPPI were scaled up to population according to the incidence of the decision.

RESULTS

At list prices, the incremental cost-effectiveness ratio was EUR 73,086 per quality-adjusted life year (QALY) (incremental costs EUR 156,928; incremental QALYs 2.15). The probability of cost-effectiveness, at the willingness-to-pay threshold of EUR 45,000 per QALY, was 16 percent. At this threshold, population EVPI was EUR 314,455; population EVPPI was below EUR 100,000 for each parameter category.

CONCLUSIONS

Tisagenlecleucel is not cost effective, versus blinatumomab, for the treatment of pediatric and young adult patients with R/R ALL in Ireland (at list prices). Further research to decrease decision (parameter) uncertainty, at the defined willingness-to-pay threshold, may not be of value. However, there is a high degree of uncertainty underpinning the analysis, which may not be captured by EVPI analysis.

Relapsed acute lymphoblastic leukaemia after allogeneic stem cell transplantation: a therapeutic dilemma challenging the armamentarium of immunotherapies currently available (case reports)

While survival rates in paediatric acute lymphoblastic leukaemia (ALL) nowadays exceed 90%, systemic ALL relapse, especially after haemopoietic stem cell transplantation (HSCT), is associated with a poor outcome. As there is currently no standardized treatment for this situation, individualized treatment is often pursued. Exemplified by two clinical scenarios, the aim of this article is to highlight the challenge for treating physicians to find a customized treatment strategy integrating the role of conventional chemotherapy, immunotherapeutic approaches and second allogeneic HSCT. Case 1 describes a 2-year-old girl with an early isolated bone marrow relapse of an infant KMT2A-rearranged B-cell precursor ALL after allogeneic HSCT. After bridging chemotherapy and lymphodepleting chemotherapy, chimeric antigen receptor (CAR) T-cells (tisagenlecleucel) were administered for remission induction, followed by a second HSCT from the 9/10 human leukocyte antigen (HLA)-matched mother. Case 2 describes a 16-year-old girl with a late, isolated bone marrow relapse of B-cell precursor ALL after allogeneic HSCT who experienced severe treatment toxicities including stage IV renal insufficiency. After dose-reduced bridging chemotherapy, CAR T-cells (tisagenlecleucel) were administered for remission induction despite a CD19^- clone without prior lymphodepletion due to enhanced persisting toxicity. This was followed by a second allogeneic HSCT from the haploidentical mother. While patient 2 relapsed around Day + 180 after the second HSCT, patient 1 is still in complete remission >360 days after the second HSCT. Both cases demonstrate the challenges associated with systemic ALL relapse after first allogeneic HSCT, including chemotherapy-resistant disease and persisting organ damage inflicted by previous therapy. Immunotherapeutic approaches, such as CAR T-cells, can induce remission and enable a second allogeneic HSCT. However, optimal therapy for systemic ALL relapse after first HSCT remains to be defined.

Cost-Effectiveness and Budget Impact Analyses of Tisagenlecleucel in Pediatric and Young Adult Patients with Relapsed or Refractory B-Cell Acute Lymphoblastic Leukemia from the Singapore Healthcare System Perspective

Purpose

Children and young adults with relapsed or refractory (r/r) acute lymphoblastic leukemia (ALL) have poor survival due to ineffective therapy options. The newly approved chimeric antigen receptor T-cell (CAR-T) therapy, tisagenlecleucel, has demonstrated improved survival but at a high up-front cost. The study aims to evaluate the cost-effectiveness and budget impact of tisagenlecleucel versus salvage chemotherapy regimen (SCR) or blinatumomab (BLN) for the treatment of pediatric and young adult patients with relapsed/refractory B-cell ALL from the Singapore healthcare system perspective.

Patients and Methods

A three-health state partitioned survival model was constructed to analyze the cost-effectiveness of tisagenlecleucel vs SCR/BLN with/without allogenic hematopoietic stem cell transplantation (allo-HSCT) over a lifetime period. Clinical efficacy for tisagenlecleucel, SCR and BLN were based on pooled data from ELIANA, ENSIGN and B2101J trials, the study by von Stackelberg et al 2011, and MT103-205 respectively. Medical costs from pre-treatment until terminal care, including treatment, side effects, follow-up, subsequent allo-HSCT and relapse, were considered. Incremental cost-effectiveness ratios (ICERs) were estimated as the incremental costs per quality-adjusted life-year (QALY) gain. Additionally, the financial impact of tisagenlecleucel introduction in Singapore was estimated, comparing the present treatment scenario (without tisagenlecleucel) with a future scenario (with tisagenlecleucel), over 5 years.

Results

In the base-case analysis, tisagenlecleucel treatment demonstrated cost-effectiveness with an ICER of S$45,840 (US$34,762) per QALY (vs SCR) and S$51,978 (US$39,315) per QALY (vs BLN). The estimated budget ranges from S$477,857 (US$361,438) to S$1.4 million (US$1.05 million) annually for the initial 5 years.

Conclusion

Tisagenlecleucel is likely to be a cost-effective treatment option with limited budget implications while treating r/r ALL patients who have failed at least 2 lines of prior therapies.

Sub-myeloablative Second Transplantations with Haploidentical Donors and Post-Transplant Cyclophosphamide have limited Anti-Leukemic Effects in Pediatric Patients

Pediatric patients with high-risk hematologic malignancies who experience relapse after a prior allogeneic hematopoietic cell transplant (HCT) have an exceedingly poor prognosis. A second allogeneic HCT offers the potential for long-term cure but carries high risks of both subsequent relapse and HCT-related morbidity and mortality. Using haploidentical donors for HCT (haploHCT) can expand the donor pool and potentially enhance the graft-versus-leukemia effect but is accompanied by a risk of graft-versus-host disease (GVHD). The goal of this protocol was to intensify the antileukemia effect of haploHCT for pediatric patients with hematologic malignancies that relapsed after prior allogeneic HCT, while limiting regimen-associated toxicities. This phase II clinical trial evaluated a sub-myeloablative preparative regimen consisting of anti-thymocyte globulin, clofarabine, cytarabine, busulfan, and cyclophosphamide, in combination with plerixafor to sensitize leukemic blasts. Participants received a mobilized peripheral blood unmanipulated haploidentical donor graft with one dose of post-transplant cyclophosphamide as GVHD prophylaxis, followed by natural killer (NK) cell addback. Here we report the clinical outcomes and immune reconstitution of 17 participants treated on the study and 5 additional patients treated on similar single-patient treatment plans. Of the 22 participants analyzed, 12 (55%) had active disease at the time of HCT. The regimen provided robust immune reconstitution, with 21 participants (95%) experiencing neutrophil engraftment at a median of 14 days after HCT. In this high-risk population, the overall survival was 45% (95% confidence interval [CI], 24%-64%), with a 12-month event-free survival of 31% (95% CI, 14%-51%) and cumulative incidence of relapse at 12 months of 50% (95% CI, 27%-69%). Four participants (18%) remain in remission at >5 years follow-up. Expected HCT-related organ-specific toxicities were observed, and 13 participants (59%) experienced acute or chronic GVHD. This intensified but sub-myeloablative regimen, followed by a high-dose unmanipulated haploidentical graft, post-transplantation cyclophosphamide, and NK cell infusion, resulted in adequate immune reconstitution but failed to overcome the elevated risks of relapse and treatment-related morbidity in this high-risk population.

Donor-derived multiple leukemia antigen-specific T-cell therapy to prevent relapse after transplant in patients with ALL

Hematopoietic stem cell transplant (HSCT) is a curative option for patients with high-risk acute lymphoblastic leukemia (ALL), but relapse remains a major cause of treatment failure. To prevent disease relapse, we prepared and infused donor-derived multiple leukemia antigen-specific T cells (mLSTs) targeting PRAME, WT1, and survivin, which are leukemia-associated antigens frequently expressed in B- and T-ALL. Our goal was to maximize the graft-versus-leukemia effect while minimizing the risk of graft-versus-host disease (GVHD). We administered mLSTs (dose range, 0.5 × 107 to 2 × 107 cells per square meter) to 11 patients with ALL (8 pediatric, 3 adult), and observed no dose-limiting toxicity, acute GVHD or cytokine release syndrome. Six of 8 evaluable patients remained in long-term complete remission (median: 46.5 months; range, 9-51). In these individuals we detected an increased frequency of tumor-reactive T cells shortly after infusion, with activity against both targeted and nontargeted, known tumor-associated antigens, indicative of in vivo antigen spreading. By contrast, this in vivo amplification was absent in the 2 patients who experienced relapse. In summary, infusion of donor-derived mLSTs after allogeneic HSCT is feasible and safe and may contribute to disease control, as evidenced by in vivo tumor-directed T-cell expansion. Thus, this approach represents a promising strategy for preventing relapse in patients with ALL.

Chimeric Antigen Receptor T-Cell Therapy in Paediatric B-Cell Precursor Acute Lymphoblastic Leukaemia: Curative Treatment Option or Bridge to Transplant?

Chimeric antigen receptor T-cell therapy (CAR-T) targeting CD19 has been associated with remarkable responses in paediatric patients and adolescents and young adults (AYA) with relapsed/refractory (R/R) B-cell precursor acute lymphoblastic leukaemia (BCP-ALL). Tisagenlecleucel, the first approved CD19 CAR-T, has become a viable treatment option for paediatric patients and AYAs with BCP-ALL relapsing repeatedly or after haematopoietic stem cell transplantation (HSCT). Based on the chimeric antigen receptor molecular design and the presence of a 4-1BB costimulatory domain, tisagenlecleucel can persist for a long time and thereby provide sustained leukaemia control. "Real-world" experience with tisagenlecleucel confirms the safety and efficacy profile observed in the pivotal registration trial. Recent guidelines for the recognition, management and prevention of the two most common adverse events related to CAR-T - cytokine release syndrome and immune-cell-associated neurotoxicity syndrome - have helped to further decrease treatment toxicity. Consequently, the questions of how and for whom CD19 CAR-T could substitute HSCT in BCP-ALL are inevitable. Currently, 40-50% of R/R BCP-ALL patients relapse post CD19 CAR-T with either CD19- or CD19+ disease, and consolidative HSCT has been proposed to avoid disease recurrence. Contrarily, CD19 CAR-T is currently being investigated in the upfront treatment of high-risk BCP-ALL with an aim to avoid allogeneic HSCT and associated treatment-related morbidity, mortality and late effects. To improve survival and decrease long-term side effects in children with BCP-ALL, it is important to define parameters predicting the success or failure of CAR-T, allowing the careful selection of candidates in need of HSCT consolidation. In this review, we describe the current clinical evidence on CAR-T in BCP-ALL and discuss factors associated with response to or failure of this therapy: product specifications, patient- and disease-related factors and the impact of additional therapies given before (e.g., blinatumomab and inotuzumab ozogamicin) or after infusion (e.g., CAR-T re-infusion and/or checkpoint inhibition). We discuss where to position CAR-T in the treatment of BCP-ALL and present considerations for the design of supportive trials for the different phases of disease. Finally, we elaborate on clinical settings in which CAR-T might indeed replace HSCT.

Incidence of subsequent malignancies after total body irradiation-based allogeneic HSCT in children with ALL - long-term follow-up from the prospective ALL-SCT 2003 trial

Total body irradiation (TBI)-based conditioning is associated with superior leukemia-free survival in children with ALL undergoing HSCT. However, the risk for subsequent malignant neoplasms (SMN) remains a significant concern. We analyzed 705 pediatric patients enrolled in the prospective ALL-SCT-BFM-2003 trial and its subsequent registry. Patients &gt;2 years received conditioning with TBI 12 Gy/etoposide (n = 558) and children ≤2 years of age or with contraindications for TBI received busulfan/cyclophosphamide/etoposide (n = 110). The 5- and 10-year cumulative incidence of SMN was 0.02 ± 0.01 and 0.13 ± 0.03, respectively. In total, 39 SMN (34 solid tumors, 5 MDS/AML) were diagnosed in 33 patients at a median of 5.8 years (1.7-13.4), exclusively in the TBI group. Of 33 affected patients, 21 (64%) are alive at a median follow-up of 5.1 years (0-9.9) after diagnosis of their first SMN. In univariate analysis, neither age at HSCT, donor type, acute GVHD, chronic GVHD, nor CMV constituted a significant risk factor for SMN. The only significant risk factor was TBI versus non-TBI based conditioning. This analysis confirms and quantifies the increased risk of SMN in children with ALL after conditioning with TBI. Future strategies to avoid TBI will need careful tailoring within prospective, controlled studies to prevent unfavorable outcomes.

Mechanisms of Immunosuppressive Tumor Evasion: Focus on Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is a malignancy with high heterogeneity in its biological features and treatments. Although the overall survival (OS) of patients with ALL has recently improved considerably, owing to the application of conventional chemo-therapeutic agents, approximately 20% of the pediatric cases and 40-50% of the adult patients relapse during and after the treatment period. The potential mechanisms that cause relapse involve clonal evolution, innate and acquired chemoresistance, and the ability of ALL cells to escape the immune-suppressive tumor response. Currently, immunotherapy in combination with conventional treatment is used to enhance the immune response against tumor cells, thereby significantly improving the OS in patients with ALL. Therefore, understanding the mechanisms of immune evasion by leukemia cells could be useful for developing novel therapeutic strategies.

MicroRNA-221 regulates cell activity and apoptosis in acute lymphoblastic leukemia via regulating PTEN

T cell acute lymphoblastic leukemia (T-ALL), an aggressive and heterogeneous malignancy originating from T cell precursors (thymocytes), accounts for ~15% of all ALL cases in children and for ~25% in adults. The present study aimed to investigate the role of microRNA-221 (miR-221) in the regulation of cell viability and apoptosis of human T-ALL cells and its related regulatory mechanisms. To perform this investigation, miR-221 was upregulated or knocked down in human T-ALL cells (Jurkat cells) using miR-221 mimic or inhibitor, respectively. Then, cell viability was determined using a 3-(4,5-dimethylthiahiazol-2-y1)-2,5-diphenytetrazolium bromide assay, cell invasion and migration were analyzed via Transwell assays, and cell apoptosis was detected using flow cytometry. It was found that transfection with a miR-221 inhibitor significantly inhibited Jurkat cell viability, migration and invasion, and induced Jurkat cell apoptosis. Whereas, transfection with the miR-221 mimic resulted in the opposite effects. Besides, the results showed that phosphatase and tensin homologue deleted on chromosome 10 (PTEN) was a target of miR-221. Moreover, it was observed that the effects of the miR-221 inhibitor on Jurkat cell viability, migration and invasion, and cell apoptosis were significantly eliminated by PTEN-small interfering RNA. In addition, it was shown that the phosphatidylinositol 3-kinase/AKT pathway was involved in the effect of miR-221 on Jurkat cells. In conclusion, the data indicated that miR-221 existed as an oncogene in T-ALL, and its downregulation could inhibit the development of ALL by targeting PTEN. Therefore, miR-221 may be a novel potential therapeutic target for ALL.

Prognostic factors for survival in children who relapsed after allogeneic hematopoietic stem cell transplantation for acute leukemia

BACKGROUND

Post-transplant relapse has a dismal prognosis in children with acute leukemia undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). Data on risk factors, treatment options, and outcomes are limited.

PROCEDURE

In this retrospective multicenter study in which a questionnaire was sent to all pediatric transplant centers reporting relapse after allo-HSCT for a cohort of 938 children with acute leukemia, we analyzed 255 children with relapse of acute leukemia after their first allo-HSCT.

RESULTS

The median interval from transplantation to relapse was 180 days, and the median follow-up from relapse to the last follow-up was 1844 days. The 3-year overall survival (OS) rate was 12.0%. The main cause of death was disease progression or subsequent relapse (82.6%). The majority of children received salvage treatment with curative intent without a second HSCT (67.8%), 22.0% of children underwent a second allo-HSCT, and 10.2% received palliative therapy. Isolated extramedullary relapse (hazard ratio (HR): 0.607, P = .011) and relapse earlier than 365 days post-transplantation (HR: 2.101, P < .001 for 0-180 days; HR: 1.522, P = .041 for 181-365 days) were found in multivariate analysis to be significant prognostic factors for outcome. The type of salvage therapy in chemosensitive relapse was identified as a significant prognostic factor for OS.

CONCLUSION

A salvage approach with curative intent may be considered for patients with post-transplant relapse, even if they relapse in the first year post-transplantation. For sustainable remission, a second allo-HSCT may be recommended for patients who achieve complete remission after reinduction treatment.

Cost-Effectiveness of Tisagenlecleucel in Paediatric Acute Lymphoblastic Leukaemia (pALL) and Adult Diffuse Large B-Cell Lymphoma (DLBCL) in Switzerland

INTRODUCTION

The purpose of the present analysis was to explore the cost-effectiveness of tisagenlecleucel in relapsed or refractory (r/r) paediatric acute lymphoblastic leukaemia (pALL) and r/r adult diffuse large B-cell lymphoma (DLBCL) in Switzerland against a range of historical standard-of-care treatments.

METHODS

Two cost-utility models were constructed for the two licensed indications using similar methodologies but indication-specific data. Clinical efficacy data were based on pooled analyses of clinical trials for tisagenlecleucel (pALL: ELIANA, ENSIGN, B2101J; DLBCL: JULIET, NCT02030834) and published data for comparator treatments. Treatment effects were compared based on matching-adjusted indirect comparison (MAIC) analyses. Four clinical lymphoma and leukaemia experts provided Switzerland-specific input regarding comparators, diagnostic and therapeutic procedures, clinical evidence and costs, which were used to inform the models. The base case analysis reflected the perspective of the Swiss mandatory health insurance system. Deterministic, probabilistic and scenario analyses were carried out to explore the robustness of results.

RESULTS

The base case analysis resulted in incremental costs of CHF 31,961-CHF 36,419 per quality-adjusted life year (QALY) gained for pALL across the different comparators and CHF 113,179 for DLBCL (1 CHF = 1.09 USD). Incremental costs per life-year gained ranged between CHF 33,906-CHF 97,399 across the two indications. Including productivity gains, tisagenlecleucel was shown to be dominant (more effective and less costly) over all the comparators for pALL and to result in incremental costs per life-year gained of CHF 57,324 for DLBCL.

CONCLUSION

Using hypothetical willingness-to-pay thresholds of CHF 100,000-150,000 per QALY gained, the present analysis has shown tisagenlecleucel to be a cost-effective treatment option in pALL and DLBCL.

[CAR T-cell therapy for children and adolescents with acute lymphatic leukemia]

BACKGROUND

Acute lymphatic leukemia is the most common malignant disease in children. Despite a good prognosis, new therapeutic concepts are needed for patients with refractory and relapsed disease.

QUESTION

The importance of chimeric antigen receptor (CAR) T‑cell therapy for patients with refractory and post-stem cell transplantation.

MATERIAL AND METHODS

Overview of studies in childhood; presentation of extraction, use, side effects and prognostic factors.

RESULTS

In 30 patients with a leukemia burden of <5% at the time of lymphocytic chemotherapy, the probability of event-free survival after 12 months was 0.70; in patients with a leukemia burden of >5%, the probability of event-free survival was only 0.23.

CONCLUSIONS

Further improvements in vector design will help to improve the effectiveness of this treatment. It will become important to isolate factors that will make it possible to identify patients who will respond to this therapy in the long term.

MicroRNA-325 inhibits the proliferation and induces the apoptosis of T cell acute lymphoblastic leukemia cells in a BAG2-dependent manner

The inhibitory effect of microRNA (miR)-325 in multiple different types of cancer cell has been identified; however, its biological function in T cell acute lymphoblastic leukemia (T-ALL) remains unknown. Moreover, Bcl-2-associated athanogene (BAG)2 is highly expressed in a various types of tumors and is regarded as an anti-apoptotic gene. In the present study, the roles of miR-325 and BAG2 in a T-ALL cell line (Jurkat cells) were investigated. BAG2 and miR-325 expression levels in clinical blood samples from healthy donors and pediatric patients with T-ALL, as well as in T-ALL cell lines was detected using western blot analysis and/or reverse transcription-quantitative PCR. Dual-luciferase reporter gene assays and TargetScan were used to evaluate the interaction between BAG2 and miR-325. Small interfering RNA technology was applied to knockdown BAG2 expression in Jurkat cells. The effects of miR-325 mimic and BAG2 downregulation on the proliferation and apoptosis were assessed by an MTT assay, flow cytometry and western blot analysis. The results revealed that the expression of miR-325 was downregulated in blood samples from pediatric patients and in T-ALL cell lines, and its expression was lowest in Jurkat cells. The expression levels of BAG2 exhibited the opposite results. The knockdown of BAG2 markedly induced the apoptosis and inhibited the proliferation of Jurkat cells. In addition, the overexpression of miR-325 significantly inhibited the growth and promoted the apoptosis of Jurkat cells, with these effects being eliminated by BAG2 overexpression. In conclusion, the findings of the present study demonstrated that miR-325 directly targets the BAG2 gene and that the introduction of miR-325 can accelerate apoptosis and suppress the proliferation of Jurkat cells by silencing BAG2 expression.

Dasatinib in the Management of Pediatric Patients With Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia

Acute leukemia is the most common cancer in childhood; in particular, acute lymphoblastic leukemia (ALL) represents roughly up to 80% of all cases of acute leukemias in children. Survival of children with ALL has dramatically improved over the last few decades, and is now over 90% (versus 40% of adult patients) in developed countries, except for in infants (i.e., children < 1 year), where no significant improvement was registered. Philadelphia positive ALL (Ph+ALL) accounts for around 3% of cases of childhood ALL, its incidence increasing with patient's age. Before the era of tyrosine-kinase inhibitors (TKIs), pediatric Ph+ALL showed a worse prognosis in comparison to other forms of ALL, and was managed with intensive chemotherapy, followed, whenever possible, by allogenic hematopoietic stem cell transplantation (HSCT) in first morphological complete remission. TKIs have revolutionized the current clinical approach, which involves combinations of imatinib plus standard chemotherapy that can abrogate the negative prognostic impact conferred by the presence of BCR/ABL1 rearrangement, resulting in the probability of event-free survival (EFS) being significantly better than that recorded in the pre-TKI era. Long-term follow-up confirms these data, questioning the role of a real advantage offered by HSCT over intensive chemotherapy plus TKI in all Ph+ALL pediatric patients. Imatinib was the first generation TKI and the prototype of targeted therapy, but over the years second- (dasatinib, nilotinib, bosutinib) and third-generation (ponatinib) TKIs showed a capacity to overcome resistance to imatinib in Ph+ hematological neoplasms. Given the effectiveness of the first-in-class TKI, imatinib, also the second-generation TKI dasatinib was incorporated in the treatment regimens of Ph+ALL. In this manuscript, we will discuss the role of this drug in pediatric Ph+ALL, analyzing the available data published to date.

Outcomes of pediatric patients who relapse after first HCT for acute leukemia or MDS

Disease relapse remains a major cause of treatment failure in patients receiving allogeneic hematopoietic cell transplantation (alloHCT) for high-risk acute leukemias or myelodysplastic syndromes (MDS). Comprehensive data on outcomes after post-transplant relapse are lacking, especially in pediatric patients. Our objective was to assess the impact of various transplant-, patient-, and disease-related variables on survival and outcomes in patients who relapse after alloHCT. We describe our institutional experience with 221 pediatric patients who experienced disease relapse after their first alloHCT for acute leukemias or MDS between 1990 and 2018. In a multivariable model, being in first complete remission at first alloHCT, longer duration of remission after alloHCT, experiencing GVHD and receiving a transplant in a more recent time period were significantly associated with a higher likelihood of receiving a second alloHCT after post-transplant relapse. Of these variables, only longer interval from alloHCT to relapse, receiving a second alloHCT or DLI, and receiving a transplant in a more recent time period were associated with improved overall survival. Our data support pursuing second alloHCT for patients who have experienced relapse after their first transplant, as that remains the only salvage modality with a reasonable chance of inducing long-term remission.

Effectiveness of T-Cell Replete Haploidentical Hematopoietic Stem Cell Transplantation for Refractory/Relapsed B Cell Acute Lymphoblastic Leukemia in Children and Adolescents

Background: The prognosis of refractory/relapsed B-cell precursor acute lymphoblastic leukemia (BCP-ALL) remains dismal owing to acquired resistance to chemotherapeutic agents. This study aimed to evaluate the efficacy of T-cell replete HLA haploidentical hematopoietic stem cell transplantation (TCR-haplo-HSCT) for pediatric refractory/relapsed BCP-ALL (RR-BCP-ALL). Methods: Nineteen pediatric patients with RR-BCP-ALL underwent TCR-haplo-HSCT between 2010 and 2019 at the Fukushima Medical University Hospital. The disease status at TCR-haplo-HSCT included complete remission (CR) in eight patients and non-CR with active disease in 11 patients. Total body irradiation-based, busulfan-based, and reduced-intensity conditioning regimens were employed in 11, 6, and 2 patients, respectively. Low-dose anti-thymocyte globulin (thymoglobulin, 2.5 mg/kg) was used in all patients. Graft-vs.-host disease (GVHD) prophylaxis was administered with tacrolimus, methotrexate, and prednisolone. Results: All patients received peripheral blood stem cells as the stem cell source. The HLA disparities in graft vs. host directions were 2/8 in one, 3/8 in five, and 4/8 in 13 patients. Among 18 patients who achieved primary engraftment, acute GVHD occurred in all 18 evaluable patients (grade II, 9; grade III, 8; grade IV, 1), and chronic GVHD was observed in 10 out of 15 evaluable patients. Three patients died because of transplant-related mortality. The 3-year overall survival (OS) and leukemia-free survival rates were 57.4 and 42.1%, respectively. Compared to patients older than 10 years in age (N = 10), those younger than 10 years in age (N = 9) showed an excellent OS rate (3-year OS rate: patients < 10 years old, 100%; patients > 10 years old, 20% [95% confidence interval, 3.1-47.5]; p = 0.002). Conclusions: We suggest that TCR haplo-HSCT with low-dose ATG conditioning has the potential to improve the transplantation outcomes in patients with RR-BCP.

ADCC can improve graft vs leukemia effect after T- and B-cell depleted haploidentical stem cell transplantation in pediatric B-lineage ALL

Posttransplant relapsed B-cell precursor ALL can be cured by 2nd hematopoietic stem cell transplantation (HSCT) in 20% of patients. The major cause of death after second HSCT is leukemic relapse. One reliable predictor for survival after 2nd-HSCT are posttransplant MRD levels. Patients with detectable or increase of MRD are likely to relapse. Patients in complete molecular remission show the best leukemia-free survival and lowest cumulative incidence (CI) of relapse. As patients who undergo second or subsequent HSCT are high-risk patients, we evaluated the prophylactic use of the chimeric Fc-optimized CD19-4G7SDIE-mAb. Posttransplant relapsed CD19⁺ BCP-ALL patients, who underwent a second or subsequent haplo-HSCT from a T- and B-cell depleted graft received posttransplant prophylactic CD19-4G7SDIE-mAb treatment on compassionate use in complete molecular remission, to increase the antileukemic activity of the new reconstituting immune system by recruiting Fc-expressing effector cells. NK cells recovered early and robust. The 3 year overall survival in 15 evaluable patients was 56%, the 3 year event-free survival was 55% and the CI of relapse 38%. Compared to a historical control group, the CI of relapse was markedly lower and consecutively the EFS higher. Posttransplant-targeted therapy may overcome the need for unspecific GvL effect of undesired GvHD, that can cause severe morbidity and mortality. Due to a low adverse event profile the CD19-4G7SDIE-mAb may be suitable for broad administration to consolidate posttransplant MRD negativity.

Tisagenlecleucel versus historical standard therapies for pediatric relapsed/refractory acute lymphoblastic leukemia

Aim: We compared outcomes from a single-arm study of tisagenlecleucel with standard of care (SOC) regimens in pediatric and young adult patients with relapsed/refractory acute lymphoblastic leukemia (ALL). Methods: The analysis included one tisagenlecleucel study, one blinatumomab study, one clofarabine monotherapy study, three studies of clofarabine combination regimens and two studies of other salvage chemotherapy. Matching-adjusted indirect comparison analyses were conducted. Results: After adjusting for baseline characteristics, tisagenlecleucel was associated with significantly prolonged overall survival compared with blinatumomab (hazard ratio [95% CI], 0.32 [0.16-0.64]); clofarabine monotherapy (0.24 [0.13-0.42]); clofarabine combination regimens (0.26 [0.15-0.45]); two salvage therapies (0.15 [0.09-0.25] and 0.27 [0.15-0.49]). Conclusion: The analysis demonstrated tisagenlecleucel was associated with substantially greater survival benefit versus all SOC regimens.

Blinatumomab and inotuzumab for B cell precursor acute lymphoblastic leukaemia in children: a retrospective study from the Leukemia Working Group of the Spanish Society of Pediatric Hematology and Oncology (SEHOP)

Blinatumomab and inotuzumab ozogamycin represent promising alternatives to conventional chemotherapy in acute lymphoblastic leukaemia (ALL). We analysed data from 29 children with ALL treated under compassionate use with blinatumomab, inotuzumab or both. The complete remission (CR) rate in a heavily pretreated population with overt relapse was 47·6%. At earlier stages (first/second CR), both antibodies represented a useful tool to reduce minimal residual disease, and/or avoid further toxic chemotherapy until stem cell transplantation. Six patients developed grade 3 reversible non-haematological toxicity. The 12-month overall survival and event-free survival rates were 50·8 ± 26·4% and 38·9 ± 25·3% with blinatumomab, 45·8 ± 26% and 27·5 ± 25% with inotuzumab.

Improved survival rate in T-cell depleted haploidentical hematopoietic cell transplantation over the last 15 years at a single institution

T-cell depletion of an HLA-haploidentical (haplo) graft is often used to reduce the risk of graft-versus-host disease (GVHD), but the lack of donor T cells in the infused product may lead to graft failure, slow T-cell reconstitution, infections, and relapse. More selective T-cell depletion targeting CD45RA can effectively deplete naïve T cells but preserve large numbers of memory T cells leading to robust engraftment of diverse T-cell populations and reduction of viremia in the early post-transplant period. Herein, we report the outcome of 143 pediatric and young adult hematologic malignancy patients receiving a first allogeneic hematopoietic cell transplantation (HCT) on 6 consecutive ex vivo T-cell depleted haploHCT protocols over the past 15 years at a single institution - including the first 50 patients on an active CD45RA-depleted haploHCT study in which patients also received NK-cells and pharmacological GvHD prophylaxis post transplant. Our data demonstrated an increase in the 3-year overall survival and event-free survival in non-chemorefractory recipients receiving CD45RA-depleted grafts (78.9% and 77.7%, respectively) compared to historic T-cell depleted haploHCT cohorts (46.7% and 42.7%, respectively, p=0.004, and 0.003). This improvement was primarily due to a reduction in transplant related mortality without significant increase in the rates of GVHD.

Highly sensitive chimerism detection in blood is associated with increased risk of relapse after allogeneic hematopoietic cell transplantation in childhood leukemia

Analysis of chimerism in blood post-HCT using STR-PCR is routinely applied in parallel with quantification of MRD to predict relapse of leukemia. RQ-PCR chimerism is 10- to 100-fold more sensitive, but clinical studies in children are sparse. We analyzed IMC in blood samples following transplantation for acute lymphoblastic or myeloid leukemia in 56 children. IMC was defined as a minimum increase of (a) 0.1% or (b) 0.05% recipient DNA between two samples. The risk of relapse was higher in children with IMC of both 0.1% and 0.05% compared to children without IMC (HR 12.8 [95% CI: 3.9-41.4; P < .0001] and 7.6 [95% CI: 2.2-26.9; P < .01], respectively). The first IMC was detected at a median of 208 days prior to relapse. The 5-year cumulative incidence of relapse for children with a single IMC was 45.5% (CI 12.3-74.4) and 41.0% (14.2-66.6) for IMC above 0.1% and 0.05%, respectively. However, in 47 and 38 children never attaining IMC > 0.1% and >0.05%, 10 and 8 children relapsed, respectively. In a landmark analysis, no association was found between IMC prior to 90 days post-HCT and subsequent relapse by either classification of IMC and AUC for RQ-PCR chimerism was 54.2% (95 CI 27.7- 84.8). Although limited by a retrospective design, these results indicate that monitoring of RQ-PCR chimerism in peripheral blood may have a role in early detection of relapse in acute childhood leukemia.

Pediatric ALL relapses after allo-SCT show high individuality, clonal dynamics, selective pressure, and druggable targets

Survival of patients with pediatric acute lymphoblastic leukemia (ALL) after allogeneic hematopoietic stem cell transplantation (allo-SCT) is mainly compromised by leukemia relapse, carrying dismal prognosis. As novel individualized therapeutic approaches are urgently needed, we performed whole-exome sequencing of leukemic blasts of 10 children with post-allo-SCT relapses with the aim of thoroughly characterizing the mutational landscape and identifying druggable mutations. We found that post-allo-SCT ALL relapses display highly diverse and mostly patient-individual genetic lesions. Moreover, mutational cluster analysis showed substantial clonal dynamics during leukemia progression from initial diagnosis to relapse after allo-SCT. Only very few alterations stayed constant over time. This dynamic clonality was exemplified by the detection of thiopurine resistance-mediating mutations in the nucleotidase NT5C2 in 3 patients' first relapses, which disappeared in the post-allo-SCT relapses on relief of selective pressure of maintenance chemotherapy. Moreover, we identified TP53 mutations in 4 of 10 patients after allo-SCT, reflecting acquired chemoresistance associated with selective pressure of prior antineoplastic treatment. Finally, in 9 of 10 children's post-allo-SCT relapse, we found alterations in genes for which targeted therapies with novel agents are readily available. We could show efficient targeting of leukemic blasts by APR-246 in 2 patients carrying TP53 mutations. Our findings shed light on the genetic basis of post-allo-SCT relapse and may pave the way for unraveling novel therapeutic strategies in this challenging situation.

Tisagenlecleucel for the Treatment of Relapsed or Refractory B-cell Acute Lymphoblastic Leukaemia in People Aged up to 25 Years: An Evidence Review Group Perspective of a NICE Single Technology Appraisal

As part of the National Institute for Health and Care Excellence's (NICE's) Single Technology Appraisal (STA) process, Novartis submitted evidence on the clinical effectiveness and cost-effectiveness of tisagenlecleucel for treating paediatric and young adult patients (under the age of 25 years) with relapsed or refractory (r/r) B-cell acute lymphoblastic leukaemia (ALL). This article presents a summary of the Evidence Review Group's (ERG's) independent review of the evidence submission, the committee's deliberations, and the subsequent development of NICE guidance for the use of tisagenlecleucel on the National Health Service (NHS) in England. Tisagenlecleucel is a chimeric antigen receptor-modified T-cell (CAR-T) product, the first of this emerging therapeutic class to be considered by NICE in this indication. The company's evidence submission was based upon three single-arm, phase II studies: ELIANA, ENSIGN, and B2101J. These trials demonstrated a beneficial effect of tisagenlecleucel, with significant extensions in event-free survival (EFS) and overall survival (OS) compared to historical control datasets on blinatumomab and salvage chemotherapy. Adverse events were common; 77% of patients suffered from cytokine release syndrome (CRS), 56% of whom required intensive care unit-level care. The ERG did not consider clofarabine monotherapy an appropriate proxy for salvage chemotherapy. The company presented a hybrid cost-effectiveness model, combining a decision tree and three-state partitioned survival model structure. The majority of quality-adjusted life-years (QALYs) gained were generated through additional life-years in the extrapolated 'long-term survival' phase of the model, where patients were assumed to be 'cured'. The ERG considered the results to be subject to substantial uncertainty, due in part to immature trial data, unresolved long-term treatment effects, and a lack of appropriate comparator data. The ERG implemented a number of changes to the company's model in an alternative base case, producing deterministic incremental cost-effectiveness ratios (ICERs) of £45,397 per QALY gained versus salvage chemotherapy, and £27,732 versus blinatumomab. The probabilistic model produced ICERs of £48,265 per QALY gained versus salvage chemotherapy, and £29,501 versus blinatumomab. The committee considered the ERG's analysis to be most closely aligned with their preferred assumptions, and did not consider tisagenlecleucel to meet both of the end-of-life (EoL) criteria. In recognition of the innovative nature of tisagenlecleucel, and the present immaturity of ongoing clinical trials, the committee considered further data collection would be valuable in resolving uncertainties around OS, the technology's novel mechanism of action, and the management of CRS and B-cell aplasia. The committee therefore recommended tisagenlecleucel for use in the Cancer Drugs Fund (CDF) until the conclusion of the ELIANA study (June 2023). This appraisal highlighted the difficulty of interpreting EoL criteria in the context of curative therapies and the valuation of cure versus extension of life. Further clarification of NICE's position in these situations may be necessary to ensure consistency and equity in their decision-making.

Allogeneic stem cell transplantation in the era of novel therapies for acute lymphoblastic leukaemia

Immunotherapy is changing the treatment of acute lymphoblastic leukaemia (ALL) in adults and children. However, regardless of these new therapies, allogeneic hematopoietic cell transplantation (allo-HCT) still play a key role in the treatment of ALL, although it is uncertain how these new therapies will impact on the transplant procedure and indications. This article reviews the indications of allo-HCT for children and adults diagnosed with ALL, the different sources and conditioning regimens for transplantation as well as the role of measurable residual diseases pre- and post-HCT in the era of the new therapies for ALL.

Molecular Approaches to Treating Pediatric Leukemias

Over the past decades, striking progress has been made in the treatment of pediatric leukemia, approaching 90% overall survival in children with acute lymphoblastic leukemia (ALL) and 75% in children with acute myeloid leukemia (AML). This has mainly been achieved through multiagent chemotherapy including CNS prophylaxis and risk-adapted therapy within collaborative clinical trials. However, prognosis in children with refractory or relapsed leukemia remains poor and has not significantly improved despite great efforts. Hence, more effective and less toxic therapies are urgently needed. Our understanding of disease biology, molecular drivers, drug resistance and, thus, the possibility to identify children at high-risk for treatment failure has significantly improved in recent years. Moreover, several new drugs targeting key molecular pathways involved in leukemia development, cell growth, and proliferation have been developed and approved. These striking achievements are linked to the great hope to further improve survival in children with refractory and relapsed leukemia. This review gives an overview on current molecularly targeted therapies in children with leukemia, including kinase, and proteasome inhibitors, epigenetic and enzyme targeting, as well as apoptosis regulators among others.

Long non-coding RNA SNHG16 has Tumor suppressing effect in acute lymphoblastic leukemia by inverse interaction on hsa-miR-124-3p

Acute lymphoblastic leukemia (ALL) is one of the deadly forms of childhood cancers in the world. In the present study, we used both in vitro and in vivo models to evaluate the functional mechanisms of a long noncoding RNA (lncRNA), small nucleolar RNA host gene 16 (SNHG16) in ALL. SNHG16 gene expression was evaluated by quantitative real-time PCR (qPCR) in both in vitro ALL cell lines and in vivo human samples of T lymphocytes. Lentivirus-mediated SNHG16 downregulation was performed in MOLT3 and SUP-B15 cells, to evaluate its functional effects on ALL cell proliferation, migration in vitro, and ALL transplant in vivo. Epigenetic regulation of SNHG16 on human miR-124-3p (hsa-miR-124-3p) was evaluated by dual-luciferase activity assay and qPCR. Hsa-miR-124-3p was inhibited in SNHG16-downregulated MOLT3 and SUP-B15 cells to further evaluate the functional correlation between SNHG16 and hsa-miR-124-3p in ALL. SNHG16 is upregulated in both in vitro ALL cell lines and in vivo human leukemic T-cells. SNHG16 downregulation suppressed ALL proliferation and migration in vitro, and ALL explant in vivo. Hsa-miR-124-3p was demonstrated to interact with SNHG16, and upregulated in SNHG16-downregulated ALL cells. In addition, inhibiting hsa-miR-124-3p reversed SNHG16-downregulation-mediated tumor suppressive functions in ALL. SNHG16 is upregulated in ALL, and its inhibition has tumor suppressive effect in ALL, likely through epigenetic interaction on hsa-miR-124-3p. © 2018 IUBMB Life, 71(1):134-142, 2019.

Second Hematopoietic Stem Cell Transplantation for Post-Transplantation Relapsed Acute Leukemia in Children: A Retrospective EBMT-PDWP Study

Outcome data were collected from the European Society for Blood and Marrow Transplantation registry on 373 children from 120 centers with relapsed leukemia (214 with acute lymphoblastic leukemia [ALL] and 159 with acute myelogenous leukemia [AML]) who underwent second allogeneic hematopoietic stem cell transplantation (HSCT) between 2004 and 2013. Overall survival (OS) was 38% at 2 years and 29% at 5 years, and leukemia-free survival (LFS) was 30% at 2 years and 25% at 5 years. Median follow-up after second HSCT was 36.4 months in the ALL group and 50.2 months in the AML group. In the ALL group, OS was 43% at 2 years and 33% at 5 years, and LFS was 34% at 2 years and 31% at 5 years. In the AML group, OS was 32% at 2 years and 24% at 5 years, and LFS was 24% at 2 years and 17% at 5 years. The 2-year nonrelapse mortality (NRM) rate was 22% in the ALL group and 18% in the AML group. Favorable prognostic factors (P < .05) for OS and LFS included >12 months between transplantations and chronic graft-versus-host disease after the first HSCT (in both groups), complete response before the second HSCT (ALL group only), and age >12 years (AML group only). Findings were more consistent over time in the ALL group, with no significant differences between 2-year and 5-year rates of relapse, NRM, and LFS. Children with relapsed acute leukemias have a substantial likelihood of long-term survival following second HSCT. Given the many novel targeted and immunomodulation therapies currently under development, it is important to identify specific patient subpopulations that may benefit from a second HSCT compared with those better suited to new approaches.

Risk Factors Influencing Outcome of Acute Leukemia Patients Who Experience Relapse After Allogeneic Hematopoietic Stem-Cell Transplantation

BACKGROUND

Prognosis of acute leukemia patients who experience relapse after hematopoietic stem-cell transplantation (HSCT) remains poor. Identifying risk factors influencing outcome of these patients is essential.

PATIENTS AND METHODS

Follow-up of 234 acute leukemia patients who underwent allogeneic HSCT from matched related donor was performed for occurrence of posttransplantation relapse. Statuses of remission and survival were assessed at 6 months after treatment of relapse. Analysis of risk factors influencing postrelapse overall survival (prOS), complete remission (CR), and nonrelapse mortality (NRM) was carried out.

RESULTS

Posttransplantation relapse occurred in 43 patients (17.9%). After treatment, 11 patients (25.6%) experienced postrelapse remission, the prOS rate was 20.9% (9 patients), and the NRM rate was 25.6% (11 patients). Older age (P = .007) and failure to experience remission after relapse treatment (P = .027) were associated with lower prOS in multivariate analysis. Female sex (P = .027), posttransplantation extramedullary relapse (P = .001), and absence of postrelapse graft-versus-host disease P = .025) were associated with lower CR rate. Also, presence of extramedullary relapse (P = .011) was associated with lower risk of NRM whereas treatment of posttransplantation relapse with donor lymphocyte infusion with or without chemotherapy (P = .002) and occurrence of postrelapse graft-versus-host disease (P = .025) were associated with higher risk of NRM.

CONCLUSION

Survival of acute leukemia patients who experience relapse after allogeneic HSCT is poor, especially in elderly patients and those who do not experience remission after relapse treatment.